AT89C2051-24PI Summary of contents

... Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C2051 is a power- ful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. ...

... I/O pin. The Port 3 output buffers can sink 20 mA. When 1s are written to Port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (I Port 3 also serves the functions of various special features of the AT89C2051 as listed below: Port Pin P3.0 P3 ...

... User software should not write 1s to these unlisted locations, since they may be used in future products to invoke new features. In that case, the reset or inactive values of the new bits will always be 0. Table 6-1. AT89C2051 SFR Map and Reset Values 0F8H B 0F0H 00000000 ...

... Programming The Flash The AT89C2051 is shipped with the 2K bytes of on-chip PEROM code memory array in the erased state (i.e., contents = FFH) and ready to be programmed. The code memory array is pro- grammed one byte at a time. Once the array is programmed, to re-program any non-blank byte, the entire memory array needs to be erased electrically ...

... RST to “L” Turn V Data Polling: The AT89C2051 features Data Polling to indicate the end of a write cycle. During a write cycle, an attempted read of the last byte written will result in the complement of the writ- ten data on P1.7. Once the write cycle has been completed, true data is valid on all outputs, and the next cycle may begin ...

... Float Waveforms Note: 1. For timing purposes, a port pin is no longer floating when a 100 mV change from load voltage occurs. A port pin begins to float when 100 mV change from the loaded V AT89C2051 14 (1) - 0.5V for a logic 1 and 0.45V for a logic 0. Timing measurements are made at V ...

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